EP-A-1 146 070 and WO-A-2007/23118 disclose impregnating with an ammonium salt and with sodium silicate, respectively, to improve the fire characteristics of melamine-formaldehyde foams. These leave something to be desired in their mechanical properties, however.
DE-A-10 2007 009127 discloses fiber-reinforced foams based on melamine-formaldehyde resins having a fiber content of 0.5% to 50% by weight. The fibrous filler used comprises short or long fibers of glass, carbon or melamine resin.
WO-A-2009/021963 discloses a process for producing an abrasive foam on the basis of a melamine-formaldehyde condensation product comprising 0.01% to 50% by weight of inorganic nanoparticles based on the weight of the precondensate.